I think the rear hub nuts on a cossie are 42mm, don't use 1/2" drive as you will snap them like carrots, use min of 3/4" pref 1" drive if you can get them, machine mart are quite good for stuff like this or look through the yellow pages for local engineering merchants or tool suppliers oh and you will be needing a big fook-off extension as well, 4-6ft at a guess, a bit of old scaffolding does the job well